Dr. Manishika Jain explains the NCERT Class 7 Geography Chapter 2: Inside our Earth\r \r Onion Peel: Demonstrating Earths Interior\r Crust\r Continental - Silica & Aluminum (SIAL) – 35 km\r Oceanic – Silica & Magnesium (SIMA) – 5 km \r B/w upper & lower crust – Conrad Discontinuity \r B/w crust & mantle – Moho Discontinuity \r Jigsaw puzzle\r Thinnest Layer\r \r \r Mantle\r About 2900 km thick\r 85% by volume\r 64% by mass\r Made of iron but mainly silicates\r Asthenosphere – Upper mantle – Convection currents \r Viscous, weak and ductile\r Just below lithosphere\r Main source of Magma\r B/w Upper & lower mantle – Repetti Discontinuity\r B/w Mantle & Core – Guttenberg Discontinuity\r Core\r Radius of about 3500 km\r Made of Iron & Nickel (NIFE)\r High temperature & pressure \r 15% of earths volume\r 32.5% of earths mass\r B/w Outer & Inner Core – Lehmann Discontinuity \r Outer Core – Liquid (Slow Moving – Produces Earths Magnetic Field)\r Pressure, Density increases towards center\r \r Rocks\r Earths Crust\r Natural mass of matter that makes the crust\r Differ in Size, Color & Texture\r 3 Types of Rocks\r Igneous\r Sedimentary\r Metamorphic\r Igneous Rocks\r Molten Magma Cools & Solidifies\r Also known as Primary Rocks\r Two Types\r Intrusive – Cools inside, Slowly cools, Forms Large grains - Granite\r Extrusive – Comes on Surface – Basalt (Deccan Plateau) – Fine Grained\r \r Sedimentary Rocks\r Rocks roll, crack & hit to break\r Sediments are transported\r Then compressed & hardened\r Sandstone – made from sand\r Red Fort – red sandstone\r Include fossils\r Metamorphic Rocks\r Igneous & Metamorphic change under heat & pressure\r Clay → Slate\r Limestone → Marble\r Taj Mahal – White Marble\r Rock Cycle – Transformation\r Minerals\r Naturally occurring substances \r Have certain physical properties \r Definite chemical composition\r Fuels – Coal, Petroleum & Natural Gas\r Industries – Iron, Aluminum\r Medicines – Calcium, Phosphorus, Magnesium\r For NCERT Based questions refer - \r \r For IAS Refer -
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